Study On Ni-ZnO/HZSM-5 Bifunctional Catalysts For Gasoline Desulfurization And Olefin Degradation

A difunctional catalyst Ni/ZnO-HZSM-5 was designes for the feature of high olefins content and high organic sulfurs content,which mainly contained thiophene and its derivatives,in the catalytically cracked gasoline?FCC?gasoline.The catalyst not only possessed the function of deep desulfurization,but also owned the function of catalyzing aromatization and isomerization of olefins,achieving desulfurization and catalytic reduction of olefins for the FCC gasoline.The catalysts were synthesized by an incipient-wetness impregnation method.In the catalysts Ni/ZnO-HZSM-5,Ni served as one of the major catalytically active sites,and ZnO played a role of sulfur capacity agent.The Ni/ZnO plays mainly role in desulfurization,and synergizes with HZSM-5 to catalyze olefin aromatization and isomerization.The interaction between metal and maxtri,crystal structure,specific surface area and the acid of the catalysts were characterized by TPR,XRD,BET and NH₃-TPD.The effects of the different the weight ratio of Ni/ZnO,the weight space velocity,the volume ratio of H₂/oil,pressure and temperature on the desulfurization and olefin reduction of catalysts were investigated respectively.And the performance of the catalysts for thiophene desulfurization and olefin aromatization including 1-pentene,2-pentene,2-methyl-2-butene and 1-hexene was investigated respectively.Through XRD,BET,NH₃-TPD and TG test and analysis,ZnAl₂O₄ spinel would not be generated in the newly synthesized or refreshed catalysts Ni/ZnO-HZSM-5.The metal sits would not destroy the structure of HZSM-5,but the strong acid on the surface of HZSM-5 almost disappears completely,for metal sits loading on the HZSM-5.Besides,almost no coke is generated on Ni/ZnO–HZSM-5 adsorbents.The optimum conditions were 420?and 2.0 MPa and the liquid hour space velocity?LHSV?was 6.0 h^-11 and H₂/oil volume ratio of 100.At optimum condition,the desulfurization rate was maintained above 98.0%,and the yield of aromatics was above 60.0%at first 3.0 hours of reaction.Different structures olefins of aromatization:1-pentene>2-pentene>2-methyl-2-butene and 1-pentene>1-hexene.It was found that reactive adsorption desulfurization besides also found that the competitive adsorption existed between olefins aromatization and thiophene desulfurization on the surface of adsorbents Ni/ZnO-HZSM-5.